This invention relates generally to software capable of transforming spatial data, and more particularly to transforming spatial data in connection with the production of maps.
A geographic information system (GIS) generally refers to a digital representation of geographically referenced information structured to support spatial analysis. While having many purposes, GIS data files have been found to be particularly useful in electronic map production. GIS data are formatted into a set of parameters that define how the data are displayed or interpreted as a map. These parameters, which typically include projection (including various subfactors, such as parallels (meridians), spheroid and zones, depending on the projection), position on screen, scale, units and angle of rotation, are collectively referred to as a “co-ordinate system.” A co-ordinate system can contain all or part of this set of parameters.
A projection is a vital part of displaying geographic data. “Projection” is a cartographic term for a mechanism (typically a mathematical algorithm) of portraying the spherical surface of the earth, or a portion thereof, on a flat surface. In displaying the earth on a flat surface some distortions of conformality, distance, direction, scale and area always result from the process; no projection is perfect. Different projections allow mapmakers to balance these various distortions, favoring one truth over another as best suited for a particular application. Every projection has advantages and disadvantages; for instance, some are better for depicting small areas while others are better for depicting large areas. There are hundreds of different projections in use today, each with its own unique formula and set of distortions.
As used herein, a transformation of spatial data refers to a change in some or all of the parameters defining the co-ordinate system in which the data is formatted. As such, a spatial data transformation is the conversion from one co-ordinate system to another. Mapmaking often requires spatial data transformations to utilize data that are formatted in different coordinate systems. For example, a first data file may contain political boundary data for a geographic area and a second data file may contain road data for the same geographic area. Using data from both files could produce a map of the geographic area showing both political boundaries and roads. However, if the two data files had different projections, then it would be necessary to “re-project” one set of data so that the projections matched. Re-projection is the mathematical process of moving spatial data from one projection to another. This can be done but typically involves a complicated mathematical process. Automated systems for achieving spatial data transformations are available but require the user to open a dialogue box and provide detailed input. Current software mechanisms that allow users to transform spatial data generally work by either providing a list of predefined projections for users to choose from, an interface to define all aspects of the projection, or a combination of the two. In all cases, however, this is a menu-driven process and requires deep knowledge and complex decision-making. This process is very time consuming and so difficult to use that users generally require special training to use it. The process must be repeated every time the user wishes to view the data in a different projection.
Accordingly, it would be desirable to have software that is capable of transforming spatial data in a more efficient and accurate manner, whether for cartographic or other purposes.